This invention is directed to a novel check valve. More particularly, this invention is directed to a backflow check valve for use with an intravenous (IV) administration set.
It has been observed that certain types of backflow check valves (such as those, for example, which are disclosed in the 2,292,003 patent to Yant et al, the 3,312,237 patent to Mon et al, and the 4,222,407 patent to Ruschke et al) wherein a disk or valve member is urged against a planar sealing surface, often develop leaks around the sealing surface. Because disks are usually cut from roll stock, they have a slight inherent curvature. Therefore, unless properly oriented, disks urged against a planar surface do not perform consistently.
As a result, some inventors have focused upon certain spatial relationships between the valve member and the sealing surface or seat. For example, in the 3,889,710 patent to Brost, it was thought essential that an abutment means be spaced from the sealing surface by more than the thickness of a disk. In the 4,354,492 patent to McPhee, another inventor thought it necessary that the valve member or disk against the valve seat be free of mechanical bias. In the 4,286,628 patent to Paradis et al, yet another inventor thought it necessary to employ prongs to pre-bias a flexible disk against a ring seat wherein flow check is achieved by engagement of the disk against a convex shoulder of the seat. For a variety of reasons, such backflow check valves also develop problems in IV use and must be replaced.
It has been observed, for example, that the use of a concave seating surface with a flotable disk is susceptible to malfunction because debris may become lodged in the concave portion of the disk. In addition, the disk may perform inconsistently depending upon its position upon the valve seat; in some positions the disk may have more flexural resistance than in others.